How to block IP Address
How to block IP Address
That's not how it works. You are getting confused between an external IP address and internal addresses. The purpose of the router is to assign each connected device its own internal IP address using something called DHCP. You can actually have up to 254 devices connected to a single router and the router will seamlessly handle assign each device its own local address, it also handles communication between internal devices. Here's a very crude network map of how the router works (gotta love MS Paint ) It is possible to override DHCP internally and manually assign addresses which can cause IP conflicts but assuming you leave DHCP alone there's no reason for conflicts to happen. This is also the reason why OPs issue cannot have anything to do with his sisters computer, the two devices are connected to the router separately from each other and therefore it is impossible for one to disrupt the others connection. Any communication between the 2 machines has to go through the router first.